Hard tissue ablation system

ABSTRACT

An electrosurgical system and method for treating hard and soft tissues in the body comprises a shaft, a distal end section, an active electrode associated with the distal end section, a first fluid supply adapted to deliver a first electrically conductive fluid to the target site, and a second fluid supply adapted to deliver a second electrically conductive fluid to the active electrode. The system is adapted to treat a wide variety of hard tissues such as, for example, bones, calcified structures, calcified deposits, teeth, plaque, kidney-stones, gall-stones and other types of tissue by generating plasma in the vicinity of the active electrode, and applying the plasma to the tissue or structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/754,551 filed May 29, 2007, which claims the benefit of ProvisionalPatent Application No. 60/809,581 filed May 30, 2006, the completedisclosures of which are incorporated herein by reference for allpurposes.

FIELD OF INVENTION

This invention relates to an electrosurgical system and method fortreating soft and hard body structures; and in particular, aradio-frequency electrosurgical system adapted for treating soft tissuessuch as ligaments and tendons, and hard tissues such as bone and othermineralized and calcified structures in the body.

BACKGROUND

A convenient and safe system to remove hard tissue such as bone is along standing challenge. Although a number of approaches exist to removebone structures including mechanical and electrosurgical devices, theapproaches have various shortcomings.

Mechanical devices such as rotary shavers have been used to clean,debride and remove bone. Rotary shavers, however, can lead to excessivebleeding. In order to control bleeding in certain orthopedic procedures,a cauterizing instrument must be utilized to control bleeding of thevarious tissues.

Electrosurgical devices such as RF tissue-cutting instruments have beenused on various hard tissue structures and deposits. However, RFelectrosurgical devices have been found to be generally ineffective atremoving bone under suitable surgical conditions.

A safe, effective, and convenient system for removing hard tissue istherefore desirable.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, an electrosurgical systemcomprises: a shaft, a distal end section, and an active electrode(s)associated with the distal end section; a first fluid supply adapted todeliver a first electrically conductive fluid in the vicinity of thetarget tissue; and a second fluid supply adapted to deliver a secondelectrically conductive fluid to the active electrode.

In another embodiment of the present invention, a method comprises:inserting an active electrode in the vicinity of the target tissue inthe presence of a first electrically conductive fluid, the firstelectrically conductive fluid provided from outside of the body;supplying a second electrically conductive fluid in the vicinity of theactive electrode; and applying electrical energy to the active electrodeto treat the target tissue.

In another embodiment of the present invention, a method comprises:delivering to the target tissue a first electrically conductive fluidsupplied from outside of the body; forming plasma from a secondelectrically conductive fluid; and treating the tissue with the plasma.

In another embodiment of the present invention, a method comprises:identifying a first tissue in a patient; delivering a first electricallyconductive fluid from outside the body to the tissue; directing a secondelectrically conductive fluid to an active electrode in the vicinity ofthe tissue; applying a radio-frequency voltage to the active electrodein the presence of the second electrically conductive fluid to generateplasma; and modifying the tissue with the plasma.

In an embodiment of the present invention, two external electricallyconductive fluid sources are provided. When a radio-frequency voltage isapplied between the active electrode and a return electrode in thepresence of the fluid, plasma is generated. Depending on a number offactors including the type of electrically conductive fluid beingsupplied, a soft tissue type may be optimally treated, e.g. ablated.Then, for example, by changing the supply of the electrically conductivefluid, a hard tissue such as a cortical layer of a bone may be ablated.Accordingly, with the present system, procedures that involve treatingboth soft and hard tissues can be accomplished with one system withoutthe need to switch from one device to another.

Details of embodiments of the present system, methods and apparatus areillustrated in the appended Figures, and described in the followingspecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an electrosurgical system with anelectrically conducting fluid source;

FIG. 2 is an illustration of an electrosurgical probe adaptable for usewith the present invention;

FIG. 3 is an illustration of an embodiment of an electrosurgical systemcomprising a plurality of electrically conducting fluid supplies;

FIG. 4 is an illustration of a distal end of an electrosurgicalapparatus immersed in first and second externally supplied electricallyconductive fluids;

FIG. 5 is an illustration of an inflamed or degenerated supra-spinatustendon;

FIG. 6 is an illustration of a rotary shaver treating an inflamedsupra-spinatus tendon;

FIG. 7A is an illustration of a device treating an inflamedsupra-spinatus tendon;

FIG. 7B is an illustration of another device treating an inflamedsupra-spinatus tendon;

FIG. 8 is an algorithm of a procedure for treating body tissue inaccordance with the present invention;

FIG. 9 is an algorithm of a procedure for treating body tissue inaccordance with the present invention;

FIG. 10 is an algorithm of a procedure for treating body tissue inaccordance with the present invention;

FIG. 11A is a cross sectional view of a distal end of an electrosurgicaldevice having an active electrode member and adapted to deliver anelectrically conductive fluid in the vicinity of the active electrode;and

FIG. 11B is a top view of the device shown in FIG. 11A.

DETAILED DESCRIPTION

An electrosurgical system (10) having only one electrically conductivefluid supply is shown in FIG. 1. It generally comprises anelectrosurgical probe (12) connected to a power supply (14) for applyinga radio-frequency voltage across an active electrode (24) and a returnelectrode (not shown) in close proximity of a target tissue, and anelectrically conductive liquid source (16) for supplying an electricallyconducting fluid (18) to the probe (12) and the target site.Electrosurgical probe (12) includes an elongated shaft (20) that may beflexible, bendable or rigid, with flexible shafts optionally includingsupport cannulas or other structures for accessing the target site.

In the system illustrated in FIG. 1, the probe (12) includes a probeconnector (22) at its proximal end and an array (24) of active electrodeterminals disposed on the distal tip of shaft (20). A connecting cable(28) comprising a handle (30) with a handle connector (32) can beremovably connected to probe connector (22). Alternatively, a cable maybe integrated with the probe (12), and connected to the power supply(14). The proximal portion of electrical cable (28) comprises anelectrical connector (34) to couple probe (12) to power supply (14).Referring to FIG. 2, an active electrode (40) and a return electrode(42) are electrically isolated from each other by an insulator (44), andeach electrode is connected to an active or passive control circuitwithin the power supply (14) by a plurality of individually insulatedconductors (not shown). A more detailed description of a system isillustrated in U.S. Pat. No. 6,142,992, which is incorporated herein byreference in its entirety. All patents and patent applications that arementioned herein are incorporated herein by reference in their entirety.

With reference to FIG. 1, power supply (14) comprises a voltageselection switch (36) to change the applied voltage level. Power supply(14) includes a mode selection switch (38) for selectively applyingpower to the electrode array (24). The foot selection switch (38) mayinclude a second pedal (not shown) for adjusting the voltage levelapplied to electrode array (24). Specific designs of a power supply aredescribed in commonly assigned U.S. Pat. No. 6,142,992, the entiredisclosure of which is incorporated herein by reference.

With reference to FIG. 2, treatment of body tissues typically comprisesplacing the active electrode (40) in close proximity to, or in contactwith the tissue, and applying the voltage across the electrodes (40, 42)to cause changes in the tissue such as heating, ablation, coagulation,cutting, removal, puncturing, and other modifications of the tissue. Inparticular, plasma may be generated in the vicinity of the activeelectrode (40) on application of the voltage to the electrodes (40, 42)in the presence of the electrically conductive fluid (18). The plasmaincludes energetic electrons, ions, photons and the like that aredischarged from a vapor layer of the conductive fluid, as described ingreater detail in commonly assigned U.S. Pat. No. 5,697,882.

In the system illustrated in FIGS. 1 and 2, the electrically conductivefluid (18) is supplied to the electrodes (40, 42) via a fluid supplylumen (46) coupled to the electrically conductive fluid supply (16). Inalternative embodiments, the system optionally includes a fluidaspiration lumen (48) for removing fluids from the target site. Invarious embodiments, the fluid-supply lumen and the fluid-aspirationlumen are connected to the elongated shaft (20) by flexible fluid lines.

With reference to FIGS. 1 and 2, the electrodes (40, 42) are located onthe distal end portion of an electrosurgical shaft (20). In thisconfiguration as is illustrated in FIG. 1, the active electrode (40) ispositioned on the shaft at or near the distal end, and the returnelectrode (42) is positioned close to, but is electrically isolated fromthe active electrode (40) by an insulator (44).

An embodiment of the present invention is illustrated in FIGS. 3 and 4.System (50) is shown comprising a probe (53) comprising a shaft (56), adistal end section (58), and at least one active electrode (60)associated with the distal end section (58); a first fluid supply (62)adapted to deliver a first electrically conductive fluid (62A) to thetarget site (52); and a second fluid supply (64) adapted to deliver asecond electrically conductive fluid (64A) to the active electrode (60).

In one embodiment the first electrically conductive fluid (62A) isselected from the group consisting of isotonic saline, buffered isotonicsaline, hypertonic saline, hypotonic saline, and Ringer's lactatesolution. In an exemplary embodiment, the second electrically conductivefluid (64A) is selected from the group consisting of sodium bicarbonate,and a mixture of sodium carbonate and sodium chloride. In anotherexemplary embodiment, the sodium bicarbonate has a concentration in therange from about 0.15 normal to about 1.0 normal sodium bicarbonatesolutions. Exemplary ratios of sodium bicarbonate/sodium chlorideconcentrations range from about 0.15 N/0.15 N to about 1.0 N/0.15 N.

The system includes a voltage supply connected to the active electrode(60) and the return electrode (68), and plasma is generated between theactive and return electrode in the presence of the electricallyconductive fluids. Each of the first and second electrically conductivefluids (62A, 64A) may be delivered through a lumen extending through theprobe. In the embodiment shown in FIG. 4, the second electricallyconductive liquid is delivered through annular-shaped lumen (54).

In various embodiments the second electrically conductive fluid supply(64) comprising a sodium bicarbonate solution is adapted to establish acurrent flow path (70) between the active electrodes (60) and the returnelectrode (68), while the first electrically conductive fluid providesan electrically conductive fluid environment around the target tissue.The first electrically conductive liquid may be delivered through anannular or other type of opening along the shaft (56). Alternatively, asdescribed in connection with FIG. 7 a, the first electrically conductiveliquid may be provided through a port or cannula independent of (andseparate from) the device (53).

In the embodiment illustrated in FIG. 3, the present system includesadjustable valves (72A, 72B) to control the flow of the first (62A) andsecond (64A) electrically conductive fluids to the target site. Thefollowing are non-limiting examples of treatment that may be performedwith the probe of the present invention: molecular dissociation,heating, ablating, coagulating, cutting, removing, excising, resecting,disintegrating, and modifications of the target site.

In the embodiment illustrated in FIG. 3, an adjustable voltage generatoris available to regulate the voltage and change the mode of operation ofthe apparatus. Thus at one voltage setting, the apparatus will generateplasma in the presence of the second conductive fluid in contact withthe active electrode; while at another voltage setting plasma generationis minimized and the apparatus causes thermal effects on the tissue suchas coagulation, contraction, and vessel hemostasis.

As indicated above, a number of types of hard and soft tissues may betreated. The following are non-limiting examples of hard tissues thatmay be modified and removed using the present invention: bone, calcifiedtissue, mineralized tissue, calcified deposits, kidney stones, gallstones, tartar deposits, teeth, calculus and plaque, ossified tissues,and the like. The following are non-limiting examples of soft tissuesthat may be treated with the present invention: ligament, tendon, bursa,fascia, muscle, intervertebral discs, cartilage, and other soft tissuesin the body.

With reference to FIG. 4, the present system in one embodiment comprisesa probe having a distal end section (58) that can be placed in contactwith (or in close proximity) to a target tissue (52). In particular, theactive electrode terminals (60) are in contact or in close proximitywith tissue (52). The environment that surrounds the working end ofprobe is filled with a first electrically conductive fluid (62A) thatmay, by way of example, be isotonic saline or other biocompatible,electrically conductive irrigant solution. The fluid environment that isin contact with the active electrode at the distal end comprises asecond electrically conductive fluid (64A) that is chemically differentfrom the first conductive fluid (62A).

The second or ancillary fluid may be, for example, a sodium bicarbonatesolution or another fluid that provides a desired tissue effect. Thefollowing are fluids that may be suitable as a second or ancillaryinjected fluid: acids, such as citric acid, phosphorous acid,hydrochloric acid, etc; bases, such as sodium bicarbonate, sodiumhydroxide, etc; chelating agents, such as ethylenediaminetetraaceticacid (EDTA), nitrilotriacetic acid, diethylenetriaminepentaacetic acid,etc; gases, such as nitrogen, helium, argon, etc; as well as hypertonicand hypotonic saline either pH buffered or unbuffered. Some of the abovementioned fluids, as well as various combinations of them, have beenfound to be effective in causing bone ablation.

The volume of fluid to provide a desired effect (e.g., bone ablation)may vary widely. Relatively small amounts (as little as a fewmm³/minute) of injected precursor fluid was sometimes effective inablating bone. Flowrates greater than 1 or 2 mm³/minute may also besuitable. Aggressive chemicals (strong acids, bases, etc) could beinjected locally to the distal end of the device, activated by theplasma, interact with the bone to cause ablation, and then beneutralized and diluted to safe levels in a surrounding bufferedisotonic saline field so that untargeted tissue was not exposed to theaggressive precursor or plasma activated chemical species.Alternatively, transient and locally aggressive chemical species formedby the plasma from relatively benign fluids may cause a desired effectas well.

In the system shown in FIGS. 3-4, when a voltage is applied between theactive electrode terminals (60) and the return electrode (68), anelectrical current flows between the active electrode and the returnelectrode along current flux lines (70). The current flux lines areshown extending through the second electrically conductive fluid in theregion above the surface of the tissue to complete the electrical pathbetween the active electrode terminals and the return electrode. As aconsequence of the applied voltage across the active and returnelectrodes in the presence of the second conductive fluid, plasma isgenerated around the active electrode and is used to treat or remove thetissue (52).

The system may also be configured to heat and coagulate tissue at adifferent voltage setting, typically lower than the ablating voltage,due to the electrical impedance of the tissue and the proper selectionof the applied voltage and current. Heating of the tissue may occur in aregion below the surface of the tissue. The present invention may beused to elevate the temperature of the tissue from normal bodytemperature (e.g. 37° C.) to a temperature in the range 55° C. to 85°C., preferably in the range from 60° C. to 70° C.

FIG. 5 illustrates one condition that may be treated using the system ofthe present invention. In particular, an inflamed supra-spinatus tendon(72) is shown. The tendon is located between the acromion process (74)and the humerus head (76). This condition may arise for a number ofreasons including, for example, excessive use during racquet sports.Friction between the tendon and the bone causes inflammation.Decompressing this region may relieve pain and is therefore desirable.

FIG. 6 illustrates decompression whereby tissue and bone is removed toreduce the pressure in the shoulder. Soft tissue including tendon (72),bursa (73) as well as hard bone (74) from the acromion are shown beingremoved with an electrosurgical shaver or burr (78). As shown in FIG. 6,several tools and instruments are required including: a rotatingmechanical instrument such as shaver (78) to remove bone defects, and anelectrosurgical tool (not shown) to treat and cauterize the soft tissue;a fluid port (80) to flush and inflate the site; and an arthroscope(80″) for visibility. As indicated above, use of a rotary shaver is notalways desirable because it may lead to excessive bleeding which maythen require a separate coagulating tool.

FIG. 7A illustrates one application of the present invention. Inparticular, a device 12 is shown being used to perform a subacromonialdecompression including the removal of various soft tissue 72.Additionally, the acromion (74) is being ablated. The whole field isfilled with a first electrically conductive fluid (which could bebuffered isotonic saline, for example). The first fluid is shown beingdelivered via tube (80′). A second electrically conductive fluid (0.65 Nsodium bicarbonate, for example) is injected through device (12) intothe vicinity of the active electrode. Without being bound by theory, thesecond fluid mixes with the first fluid, and is more highly concentratedat its point of injection (300). The plasma that discharges in thehighly concentrated second fluid near the active electrode form chemicalconditions that are particularly effective at ablating bone at thetarget site. It is thought that as this second fluid dissipates in thesurrounding first fluid the plasma decays and the solution becomes pHneutralized and diluted to levels that are not harmful to surroundinguntargeted tissue. In this manner, the acromion is ablated to furtherrelieve pressure or decompress this area.

Additionally, the device (12) has the capability to debride or ablatesoft tissues prior to, or after performing the acromioplasty. One way toablate the soft tissue using device (12) is to shut off the flow of thesecond liquid. The plasma shall therefore form around the activeelectrode by vaporizing the first electrically liquid which may, forexample, be only effective against one type of tissue such as a tendon,or another tissue.

Depending on the voltage difference applied between the active and thereturn electrode as indicated above, at any point in time, the device(12) may provide coagulation to halt or arrest bleeding of tissues. Inthis embodiment, the system of the present invention can decompress theshoulder including sculpting soft tissue, sculpting bone, andcoagulating or arresting bleeding.

FIG. 7B illustrates another embodiment of the present invention. Inparticular, device (12) includes two lumens extending through the shaftof the device corresponding to a first and second electricallyconductive liquid supplies. However, it is to be understood thatadditional lumen may be provided for additional fluid delivery oraspiration. The target site is shown flooded, immersed, or irrigatedwith the first electrically conductive liquid such as isotonic salineusing the first lumen. A second electrically conductive liquid,different than the first liquid, is also injected into the target sitethrough the second lumen. The second electrically conductive liquid isinjected preferable near the active electrode such that it is highlyconcentrated at the point of injection as described above in connectionwith FIG. 7A. The plasma formed from the second liquid provides enoughenergy to ablate or molecularly disassociate hard tissue and bone (74).At any point, the flow of the second electrically conductive fluid maybe halted, and the device may be activated to treat the soft tissueusing the first or another electrically conductive liquid.

FIG. 8 illustrates a method in accordance with the present inventioncomprising the steps of: (82) inserting an active electrode in thevicinity of the target tissue (72, 74) in the presence of a firstelectrically conductive fluid, the first electrically conductive fluidprovided from outside of the body; (84) supplying a second electricallyconductive fluid in the vicinity of the active electrode; and (86)applying electrical energy to the active electrode to treat the targettissue (72, 74).

In an alternative embodiment, the tissue (72, 74) is treated by themethod (90) set forth in FIG. 9, comprising the steps of: (92)contacting the target tissue (72, 74) with a first electricallyconductive fluid (62A) supplied from outside of the body; forming plasmafrom a second electrically conductive fluid (64A) around an activeelectrode (60) in close proximity of the tissue; and treating the tissuewith the plasma.

In a further embodiment illustrated in FIG. 10, the tissue (72, 74) istreated by a method (100) comprising the steps of: (102) identifying thetissue in the body; (104) flooding the tissue with a first electricallyconductive fluid from outside the body; (106) directing a secondelectrically conductive fluid to an active electrode in the vicinity ofthe tissue; (108) applying a radio-frequency voltage to the activeelectrode in the presence of the second electrically conductive fluid togenerate plasma in the vicinity of the active electrode; and (110) usingthe plasma to modify the first tissue.

The present system and methods are adaptable to treat tissues havingvarious hardness. For example, in treating an articular joint or theacromial bone the soft tissue is first treated by applying a firstvoltage difference between the active and return electrode in thepresence of the electrically conductive fluid. Then, without changingthe probe, and using for example a sodium bicarbonate solution, a hard,bony tissue or structure may be modified, ablated or otherwise treated.In an alternative procedure, the hard tissue may be treated prior totreating the soft tissue. In another embodiment of the presentinvention, both hard and soft structures are treated contemporaneously.Additionally, hemostasis or coagulation may be effected by varying thevoltage difference applied between the electrodes.

In another embodiment of the present invention, a visual indicator isincluded in each conductive fluid to allow a surgeon to quicklydistinguish one plasma type from another. An agent may be added to eachof the conductive liquids that produces a unique color of plasma. Forexample, potassium chloride tends to produce a purple colored plasmawhen added to the first electrically conductive liquid and anotherchemical (e.g., copper II chloride for bright green, or manganese IIchloride for yellow-green) may be added to the second electricallyconductive liquid. Thus, the surgeon may observe which mode (or plasmatype) is active during a procedure by observing the color of the plasmaat the tip of the probe. This safeguards against applying an impropertype of plasma (or voltage scheme) on a particular tissue. Indeed, useof one type of plasma may be too aggressive for one type of tissue.Also, use of one type of plasma may be highly ineffective againstcertain types of tissues or structures.

A manually or electrically controlled valve may be incorporated into theprobe, or tubing line to provide various flow rates and mixtures offluids. While simple fluid injection pressures may be effected usinggravity, more advanced pumps may be provided to carefully control theflow rate. Also, the flowrate and injection manifold design may beadjusted to provide a jet-like effect. In one embodiment, fluid flowrates of the second or ancillary fluid may be in the range of about 5ml/minute to about 65 ml/minute.

EXAMPLE

One embodiment of the present invention was used to treat a porcine ribcortical bone. The bone was immersed in a first static electricallyconductive fluid. A second ancillary liquid comprising a 0.5 N sodiumbicarbonate and 0.9% (w/w) sodium chloride (unbuffered) was disposedaround an active electrode. The device was similar to the probe (200)shown in FIG. 11A,B. The ancillary liquid was injected around the activeelectrode at flow rate of about 5 milliliters per minute through lumen(202). The first static solution comprised buffered isotonic saline(0.9% w/w NaCl in water, buffered to pH=7.0-7.2). A voltage ofapproximately 390 volts rms (root mean square), 551 volts amplitude wasapplied across the active electrode (204) and the return electrode(206), while the electrode (204) was moved over the bone with lighttactile force. After 1 minute of treatment the voltage was turned offand the sample examined. A bone removal rate of approximately 72.8 cubicmillimeters per minute was determined from the dimensions of the zone ofremoved bone and the treatment time.

A wide variety of surgical applications may be performed using theprobe, system and methods of the present invention including, but notlimited to: endovascular surgery, peripheral vascular surgery, coronaryvascular surgery, (e.g., atherectomy), spine surgery (e.g., discectomy),orthopedic surgery (e.g., acromioplasty, subacromial decompression),craniofacial surgery, oral surgery (e.g., tonsillectomy), urologicsurgery (e.g., calcific stone removal), dental specialties includingendodontics, periodiontics, and general dentistry.

By the present description and Figures it is to be understood that theterms used herein are descriptive rather than limiting, and thatchanges, modifications, and substitutions may be made without departingfrom the scope of the invention. Therefore the invention is not limitedto the embodiments described herein, but is defined by the scope of theappended claims.

Additionally, all features and aspects of the above describedembodiments and examples may be combined with other aspects and examplesset forth above. All such combinations that are not mutually exclusiveare also part of the present invention.

1. An electrosurgical system for treating a target structure in apatient, comprising: a device comprising a shaft, a distal end section,and an active electrode associated with the distal end section; a firstfluid supply adapted to deliver a first electrically conductive fluid inthe vicinity of the target tissue; and a second fluid supply adapted todeliver a second electrically conductive fluid to the active electrode.2. The electrosurgical system of claim 1, wherein the first electricallyconductive fluid is selected from the group consisting of: isotonicsaline, hypertonic saline, hypotonic saline, and Ringer's lactatesolution.
 3. The electrosurgical system of claim 1, wherein the secondelectrically conductive fluid comprises sodium.
 4. The electrosurgicalsystem of claim 3, wherein the sodium bicarbonate fluid comprises aconcentration of sodium bicarbonate in the range from about 0.15 normalto about 1.0 normal.
 5. The electrosurgical system of claim 1, wherein avoltage supply is connected to the active electrode.
 6. Theelectrosurgical system of claim 5, wherein plasma is generated uponapplication of the voltage to the active electrode.
 7. Theelectrosurgical system of claim 1, wherein the shaft comprises anaspiration lumen adapted for removing fluids from the target site. 8.The electrosurgical system of claim 1, wherein the first and secondelectrically conductive fluids are delivered through a plurality oflumens on the shaft.
 9. The electrosurgical system of claim 1, whereinthe shaft comprises a return electrode.
 10. The electrosurgical systemof claim 9, wherein the second electrically conductive fluid comprises acurrent flow path between the active electrode and the return electrode.11. The electrosurgical system of claim 1, wherein a valve controls theflow of the second electrically conductive fluid.
 12. The system ofclaim 5, wherein an adjustable voltage generator regulates the voltageto cause at least one of: molecular dissociation, heating, ablating,coagulating, cutting, removing, and modifications of the target tissue.13. The system of claim 1, wherein the first electrically conductivefluid supply is delivered through a lumen integral with the device. 14.An electrosurgical apparatus for treating a target structure in apatient, comprising: a device comprising a shaft, a distal end section,and an active electrode associated with the distal end section; and afluid source adapted to deliver a sodium bicarbonate solution in thevicinity of the active electrode.
 15. The electrosurgical system ofclaim 14, wherein the sodium bicarbonate solution comprises from about0.15 normal to about 1.0 normal sodium bicarbonate.
 16. Theelectrosurgical system of claim 14, wherein a voltage supply isconnected to the active electrode.
 17. The electrosurgical system ofclaim 16, wherein plasma is generated off the active electrode uponapplication of the voltage to the active electrode.
 18. Theelectrosurgical system of claim 16, wherein the sodium bicarbonatesolution is delivered through a lumen on the shaft.
 19. Theelectrosurgical system of claim 16, wherein the shaft comprises a returnelectrode.
 20. The electrosurgical system of claim 19, comprising acurrent flow path between the active electrode and the return electrodeestablished by the presence of said sodium bicarbonate solution.